X-Pro 1 memory card advice

I pulled the trigger on a X-Pro 1 on Sunday. Now, as I wait for it to arrive I am looking to buy a memory card for it. I am sure a 16gb would be fine but I will buy a larger card if a good price can be had. My bigger concern is speed. I have a preference for SanDisk cards. I don't want to waste money buying a card that is overkill but I don't want to end up with a card that is to slow. Any advice?